The experiments proposed here will continue investigations of central nervous system areas important in the control of fluid galance and blood pressure. The subfornical organ, an identified site of action of angiotensin II, and the preoptic nucleus medianus will be studied for their roles in salt intake, water intake, vasopressin secretion, and sodium and water excretion. Experiments will directly manipulate these forebrain structures through lesion and injection techniques. The effects of these brain manipulations on fluid and cardiovascular parameters will be studied. Behavior as well as autonomic and endocrine functions will be assessed. These areas form an integral system in the forebrain which exerts a control over fluid and cardiovascular function, and may be involved in the development of certian forms of hypertension.